Moisture management is defined as “The controlled movement of water vapor and liquid water (perspiration) from the surface of the skin to the atmosphere through the fabric” (See Cotton Incorporated, Cary N.C., 2002, 100% Cotton Moisture Management, Journal of Textile And Apparel, Technology and Management, Vol. 2., Issue 3). Moisture management is a key property that determines the comfort parameters of a fabric since poor moisture management can lead to problems such as a wet feeling fabric, a high humid microclimate between the skin and the fabric, clinging of the fabric, etc. Efficient moisture management may depend on efficient moisture absorption, transport and evaporation properties of a fabric (See Wang, L., Li, C., 2005, A new method for measuring dynamic fabric heat and moisture comfort, Experimental Thermal and Fluid Science 29, pp. 705-714; Li. Chuang, 2001, Research on Dynamic Thermohydro-Comfort Property of Textiles, Shanghai Textile Science & Technology 29 (2) pp. 53-55; L. Fourt, N. R. S. Holloes, 1984, The Comfort and Function of Clothing, Textile Industry Press, Beijing; AATCC review, March 2004 Moisture Management: Myths Magic and misconception. William A. Reack. p. 42).
Consumers prefer functional textiles or fabrics, which are, at the same time, comfortable. While functional fabrics have many desirable properties, moisture management or water transport has become the primary standard for functional fabrics. Moisture management fabrics have attracted great interest in the textile industry since this property has become more popular in garments and apparel produced for active-wear applications. Currently, efficient moisture management systems are mainly fabricated with synthetic fiber types such as nylon and polyester. These moisture management systems are added to the fabric in the manufacturing stage.
Fabrics with moisture management properties can transport moisture from the wearer's skin surface into the surface of the fabric, and then release the moisture to the atmosphere. Accordingly, such functional fabrics transport sweat and moisture from the surface of the skin to the outer surface of the fabric. This keeps the wearer's body dry and comfortable and helps the fabric from clinging to the wearer's body. Some fabrics with good moisture management properties are made from polyamide (PA) or polyester (PE). These fabrics are lightweight, absorb moisture quickly, and remove the moisture from the fabric rapidly.
However, natural fiber types such as cotton are highly preferable among wearers since these fiber types often exhibit perfect optical, thermal, mechanical and electrical properties as suited for clothing applications unlike certain synthetic fiber types. Despite these advantages these fibers are known to accumulate relatively large amounts of moisture as compared to synthetic fibers due to their hydrophilic nature (See Cotton Incorporated, Cary N.C., 2002, 100% Cotton Moisture Management, Journal of Textile And Apparel, Technology and Management, Vol. 2., Issue 3). In addition, many natural fiber types also show very slow wicking and drying rates, leading to poor moisture management properties. Id.
The human body releases moisture in the form of perspiration and sweat. Some fabrics act as a buffer between the skin and the environment and a fabric's properties will determine the conditions of the microclimate between skin and the fabric. During sweating, this microclimate can be saturated with water vapor and can have a higher relative humidity than the external environment. Since relative humidity of the microclimate is what is felt by the wearer, it is important to regulate this microclimate at a level comfortable to the wearer. To remain comfortable, a good fabric must have improved performance, especially in wicking property, moisture vapor transmission (Breathability), transer of water and faster drying. Effective moisture management of a fabric will depend mainly on its ability to transport moisture away from the inner side of the fabric to the outer surface where more spreading and evaporation occurs. To achieve these goals, the fabric should demonstrate enhanced wicking power while having more absorbent capacity of water in the outer surface of the fabric than the inner side. It should also have the ability to transport moisture vapor more effectively through the fabric, so that humidity equilibrium between skin and environment is kept at a point which is not uncomfortable to wearer.
Reducing a fabric's effective moisture absorbent capacity is the most widely used method to improve moisture management properties. This is achieved by blending certain amount of hydrophobic fibers to the fabric during the fabrication stage. This improves the wicking of the fabric and reduces the amount of water needed to saturate the fabric thus providing fast moisture transport across the fabric and reduced drying time. A slightly different approach uses localized regions of less moisture absorbency through chemical treatments. This technology is known as wicking windows technology (See Cotton Inc. Wicking Windows™.
Moisture management fabrics are also fabricated using denier differential techniques which produce two layers of fibers having different fiber sizes. Since the wicking is a capillary effect essentially facilitated by smaller fiber sizes, the technique produces a fabric having two distinct wicking regions. Inner surface is typically made with fibers having small fibers and the outer surface is made with larger fiber sizes which facilitate the wicking from inner surface to outer surface (See WO 2012/096920).
Fabrics with moisture management properties can be constructed with fibers having special fiber morphologies. These fiber cross sections are especially designed to have capillaries on their surface thus improving the rate of wicking.
To the best of our knowledge, improvement of the moisture management properties of cotton using any form of super absorbent nanofibers has not been reported. Pommet and Gardner showed that the surface modified cellulosic fibers with cellulose nanofibers have improved mechanical properties. (See M. Pommet, J. Juntaro, J. Y. Y. Heng et al., “Surface modification of natural fibers using bacteria: depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced anocomposites,” Biomacromolecules, vol. 9, no. 6, pp. 1643-1651, 2008; D. J. Gardner, G. S. Opor to, R. Mills, and M. Samir, “Adhesion and surface issues in cellulose and nanocellulose,” Journal of Adhesion Science and Technology, vol. 22, pp. 545-545, 2008).
However, the effect of cellulose nanofibers on the moisture management properties of a fabric made from these fibers was not investigated. Ting has evaluated the effect of cellulose nano powders on the cotton fabrics has and reported that the fabric shows better moisture management properties compared to normal cotton (See YingTing Guan and Yi Li, ‘Fabrication of cotton nano-powder and its textile application’ Chinese Science Bulletin, Volume 53, Number 23, 3735-3740).
These reported methods can be mainly classified in to two different groups. First, moisture management effect is obtained with the aid of especially designed fabric structures. Typically, these structures use more a hydrophobic yarn arrangement near the skin and more hydrophilic yarn arrangement towards the outer side. Due to hydrophobic nature of the inner surface, fabric tends to be relatively dry under sweating conditions. The hydrophilic yarn arrangement in the outer surface can absorb the moisture wicked away from hydrophobic region. (See U.S. Pat. Nos. 5,217,782, 6,427,493, 6,432,504, 7,217,456, U.S. 2003/0182922, U.S. 2005/0188470, U.S. 2005/0239361, U.S. 2006/0148356, U.S. 2007/0034278, U.S. 2008/0128044, U.S. 2008/0289090, and U.S. 2009/0104427).
Others suggest the use of especially designed yarn types to be used as potential materials. Capillary structures were built in to the yarn morphology and these structures are known to assist in wicking of the fabric. U.S. Pat. No. 6,509,285 and U.S. 2006/0148349 suggest similar techniques to enhance moisture management.
In view of the above, it is desirable to provide a moisture management fabric that will exhibit sought-after comfort and mechanical attributes, while at the same time being able to efficiently transfer moisture away from the wearer.